A conventional electric discharge machining system includes a first comparison device that compares the integral of high frequency components of an electric discharge pulse with a reference value, a second comparison device that compares the integral of high frequency components of the electric discharge pulse with a reference value lower than that for the first comparison device, a machining-voltage-level detector that detects a discharge voltage level of a machining gap between an electrode and a workpiece, a comparator that compares an output signal of the machining-voltage-level detector with a reference voltage, a discharge detector that detects discharge voltage and a discharge current of the machining gap between the electrode and the workpiece, and a short-circuit detector that detects a short circuit.
In this electric discharge machining system, as determination outputs classified for each pulse, a pulse controller receives the electric discharge pulse determination outputs from the first comparison device, the second comparison device, and the comparator and two kinds of determination output from the short-circuit detector indicating presence or absence of a short circuit. Then, in a case when an output signal of the short-circuit detector indicates a non-short-circuited discharge pulse and the second comparison device outputs a signal of “H” level, the pulse controller determines that the pulse is an abnormal discharge pulse caused by a high frequency component, to change a suspension time to Toff+ΔToff. In a case when an output signal of the discharge detector indicates “being in electric discharge pulse”, and the comparator outputs an output signal of “H” level, the pulse controller determines that the pulse is an abnormal discharge pulse based on a machining voltage level, to terminate the pulse of the discharge voltage and current. In a case of a non-short-circuited normal pulse, the suspension time is controlled to be reset to that before change. As described above, a system has been proposed in which the discharge state is recognized by a high frequency component and a discharge voltage level, so that electric discharge pulses are individually and optimally controlled according to presence or absence of a short circuit state (refer to Patent Document 1).